We have data indicating that corticosterone implants in the central nucleus of the amygdala may increase the freezing response of rats exposed to a stress. We are currently analyzing these results and correlating them with histological inspections of the implantation sites. This will complete phase I of this project. Moreover, Dr. Li-Xin Zhang has worked intensively on his technique of neuronal transfection with the adeno-associated virus modified to express the antisense cDNA complementary to a gene or mRNA of interest -- in this case the glucocorticoid receptor gene, the CRF receptor, and CRF itself. We will undertake intracerebral injections of the plasmid constructs generated, as mentioned above, with the help of Dr. Zhang. The upcoming departure of Dr. Philip Holmes next July will force us to modify phase II of this project and we will study fear-potentiated startle instead of freezing in order to asses the impact of the glucocorticoid receptor, CRF, and CRF receptor modulation on the central nucleus of the amygdala and other limbic structures.